| 摘要 |
PURPOSE:To increase the number of information recordable on one place by using a recording layer formed of plural colorants having a property by which the half-value width of light absorption is narrowed by association and also having different light absorption wavelength regions. CONSTITUTION:Light sources 8-11 give off selectively light of wavelengths of 570, 590, 620, and 640nm and are turned ON-OFF separately by input signals. A light collector 12 focuses a beam of light on a rotary photo-recording medium 7 with recording layers 2-5 from light sources 8-11, and a branching filter 13 distributes light rays for every wavelength into original four beams and converts them into electrical signals by sensors 14-17. When light sources 8 and 9 are turned ON, only the portion exposed to light in the recording layers 2 and 3 is heated and colorants are decomposed to record '1'. During the reproducing period, when irradiation of light sources 8-1 is made with an intensity corresponding to 1/10 of that during the writing period, the intensity of corresponding wavelength of light permeated is varied according to whether or not colorants are decomposed in the recording layers 2-5, and they are taken out as 4-bit electric signals by sensors 14-17. |
